Just got back from the vet because my dog got into my roommates stash. Good news—she’s going to be fine, but she’s going to be deeply stoned for a long, long time.
Once you have crossed a certain amount of ingested THC it only prolongs the effects but doesn't make them stronger. I've heard of people being high for over 24 hours from a miscalculated edible dosage
Either can make them very ill/cause death (in extremely high dosages), but the effects are different. Even if they don't eat things with the THC psychoactive qualities having been unlocked from heat being applied, they can still "look" like they're very stoned, when in fact, they're just very, very sick.
Dogs tend to hide all sick-like behaviors similarly. It's just one of those evolutionary instinctual things they do to not show weakness that could get them removed from a pack (or so I've read).